You may find that when you paste a link to a Google Doc (Slides, Sheets, Docs, etc.) that other users can't see it.
In order to allow other people to see your Docs you must set the "Share" settings to be "publicly visible" or "editable".
Navigate to the Google Doc in question in your web browser.
(Safari, Explorer, Chrome, Firefox, etc.)
1. Click in the top right of the document.
2. Clickin the top right of the window.
3. Change to "can edit if desired"
4. Copy the link to Paste into Virbela